This invention relates to an impact printer and more particularly to such a printer capable of generating high quality line alphanumeric characters made up of discrete dots or pels.
Various types of high speed printers have been devised for generating a so-called hard copy or paper output from various data and word processing machines, e.g., high speed digital computers. Among these various types is one class of printing mechanism often referred to as a pin printer. Typically, in these devices, a print head carrying a plurality of impact pins arranged in a vertical column is traversed across the paper and the pins are actuated in an organized sequence to create recognizable characters. By and large the actuation of the pins is controlled in accordance with a uniform matrix pattern, e.g., a 5.times.7 matrix in which a pin strike or dot may be produced or not in any one of the 35 squares of the matrix. A 7.times.9 matrix providing 63 such possible strike points is also frequently used. It has also been proposed to utilize so-called half-space positions for certain dots used in various characters, e.g., as proposed in U.S. Pat. No. 3,627,096 issued Dec. 14, 1971 to Edward D. Finnegan. In the use of each of these prior art systems, however, the matrix origin of the resultant characters is manifestly palpable and the resultant product is readily identifiable as computer produced. The impression created on the observer is thus entirely distinguishable from that created by fine printing or high quality typing as such would expect from a law office. Accordingly, though impact pin printers have many inherent advantages, including low cost and high speed, such printing devices have not been acceptable in most word processing environments. Rather, various single-element printing mechanisms have predominated despite their higher cost, lower speed and greater complexity.
Among the several objects of the present invention may be noted the provision of a method and apparatus for generating high quality alphanumeric characters utilizing an impact pin printing head; the provision of such a method and apparatus which will generate curved and inclined lines with acceptably smooth edges; the provision of such a method and apparatus which will operate at high speed as compared with single-element printing devices; the provision of such apparatus which is highly reliable and which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.